Duct Testing - is a change in order? - Home Energy Pros2016-12-09T14:03:00Zhttp://homeenergypros.lbl.gov/forum/topics/duct-testing-is-a-change-in-order?groupUrl=bestpracticesresidential&commentId=6069565%3AComment%3A140046&xg_source=activity&groupId=6069565%3AGroup%3A2238&feed=yes&xn_auth=noGot you - thanks for the expl…tag:homeenergypros.lbl.gov,2015-08-06:6069565:Comment:1854962015-08-06T23:34:27.113ZSean Lintow Srhttp://homeenergypros.lbl.gov/profile/sls
<p>Got you - thanks for the explanation</p>
<p>Fortunately for most if anyone is anywhere close to that mark they have failed in a big way (or someone missed sealing a few covers)</p>
<p>Got you - thanks for the explanation</p>
<p>Fortunately for most if anyone is anywhere close to that mark they have failed in a big way (or someone missed sealing a few covers)</p> Duct surface area clearly giv…tag:homeenergypros.lbl.gov,2015-08-06:6069565:Comment:1856342015-08-06T16:25:37.656ZBrennan Lesshttp://homeenergypros.lbl.gov/profile/BrennanLess
<p>Duct surface area clearly gives the more precise assessment of the quality of the installed duct system. But that precision is only precise in appearance, due to the difficulties of getting the correct surface area number. This is similar to blower door testing and reporting of floor area or volume normalized values (cfm50/ft2 or ACH50) vs. normalized by surface area (cfm50/ft2SA). The latter better characterizes the quality of the envelope, but it is harder to assess (easier than duct…</p>
<p>Duct surface area clearly gives the more precise assessment of the quality of the installed duct system. But that precision is only precise in appearance, due to the difficulties of getting the correct surface area number. This is similar to blower door testing and reporting of floor area or volume normalized values (cfm50/ft2 or ACH50) vs. normalized by surface area (cfm50/ft2SA). The latter better characterizes the quality of the envelope, but it is harder to assess (easier than duct surface area), and the other values actually relate better to other isseus we care about, like infiltration rates and energy use. </p>
<p>That being said, the real reason I think that duct leakage normalized to the home's floor area is acceptable, is that as the requirements for duct leakage improve and approach 0, it no longer matters what you normalize to. Tight ducts will have low % leakage by either metric. </p>
<p>As for encouraging certain design and installation behaviors, I don't honestly think that very many contractors are selecting their duct materials or layout design, based on a strategy to game duct airtightness requirements. </p>
<p>Cheers.</p> The purpose of my question wa…tag:homeenergypros.lbl.gov,2015-08-05:6069565:Comment:1856062015-08-05T22:33:04.780ZColin Gengehttp://homeenergypros.lbl.gov/profile/ColinGenge
<p>The purpose of my question was somewhat different and doesn't apply to your particular test but can be a huge source of errors for many testers.</p>
<p>The foregoing does NOT apply when you attach the Blaster to the cabinet. </p>
<p>When the Duct Blaster is attached to the return via the flex duct and you read over 650 CFM on Open Range, there is good chance the Blaster is well into the NO GO zone. The manual specifically states not to go over 100 Pa back pressure but when you get to 650 CFM…</p>
<p>The purpose of my question was somewhat different and doesn't apply to your particular test but can be a huge source of errors for many testers.</p>
<p>The foregoing does NOT apply when you attach the Blaster to the cabinet. </p>
<p>When the Duct Blaster is attached to the return via the flex duct and you read over 650 CFM on Open Range, there is good chance the Blaster is well into the NO GO zone. The manual specifically states not to go over 100 Pa back pressure but when you get to 650 CFM you're usually up to around 250 Pa backpressure which is well above it calibrated range. In the last TEC Webinar they warned to measure the back pressure to ensure you don't go above 100 Pa.</p>
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<p>Here is what happens when you do. Open range starts to read high by about 10% at 600 CFM and by the time you reach 750 CFM you might be at 100% error. When you get to around 840 CFM flow stops altogether and the backlpressure on your Blaster is around 450 Pa. To prove this to yourself, simply turn your Blaster up to full speed with no flex, on Open Fan with the back of the Blaster on the floor. You will read around 840 CFM where clearly the flow is zero. </p>
<p>This is an extreme case but I have had several people swear they were reading 850 CFM on Open Fan on a flex. </p>
<p>The solution to the dillemma is super simple. Always use Ring 1 which will provide almost exactly the same flow as Open anyway but is not subject to this problem. This is a training issue that should be demonstrated to ensure Blasters are used correctly. When they are, they work fine. I would suggest never using Open Fan on the Flex. Works fine on the equipment cabinet for all the experiments I have done but I have not gone up to 1500 CFM although duct leakage at that flow rate is no longer a duct anyway. </p> In day to day operation, the…tag:homeenergypros.lbl.gov,2015-08-05:6069565:Comment:1852972015-08-05T21:46:58.100ZJohn Nicholashttp://homeenergypros.lbl.gov/profile/JohnNicholas
<p>In day to day operation, the blower is the source of pressure in the supply system and relatively depressurized return. The Static is slightly higher near the source of pressure then at the far end.</p>
<p>Hooking the test fan to the blower compartment is a better representation of the pressure at the point of leakage then at the return. </p>
<p>In day to day operation, the blower is the source of pressure in the supply system and relatively depressurized return. The Static is slightly higher near the source of pressure then at the far end.</p>
<p>Hooking the test fan to the blower compartment is a better representation of the pressure at the point of leakage then at the return. </p> Ok I will bite especially as…tag:homeenergypros.lbl.gov,2015-08-05:6069565:Comment:1855372015-08-05T12:52:07.381ZSean Lintow Srhttp://homeenergypros.lbl.gov/profile/sls
<p>Ok I will bite especially as many parts of the country have a single return which is where testing should be done from - the exclusion for most comes with multiple returns. I have run the tests both ways &amp; the numbers are almost identical - the only thing connecting to the AH has is cutting out the leakage from the door of the AH which if installed properly should be near 0 anyways</p>
<p>Ok I will bite especially as many parts of the country have a single return which is where testing should be done from - the exclusion for most comes with multiple returns. I have run the tests both ways &amp; the numbers are almost identical - the only thing connecting to the AH has is cutting out the leakage from the door of the AH which if installed properly should be near 0 anyways</p> Yes, I was connected to the…tag:homeenergypros.lbl.gov,2015-08-04:6069565:Comment:1853712015-08-04T02:36:09.682ZJohn Nicholashttp://homeenergypros.lbl.gov/profile/JohnNicholas
<p>Yes, I was connected to the AH cabinet. I find it easier in this area, given the common mechanical set ups. Where I've tried going into a return, I usually have gravity to fight. &lt;GRIN&gt;</p>
<p>I did a guarded Blower Door Test with my QAD on a duplex unit. He set up his duct blaster as well for the fun of it. I went into the cabinet and he went into a ceiling return. It worked for him. </p>
<p>Yes, I was connected to the AH cabinet. I find it easier in this area, given the common mechanical set ups. Where I've tried going into a return, I usually have gravity to fight. &lt;GRIN&gt;</p>
<p>I did a guarded Blower Door Test with my QAD on a duplex unit. He set up his duct blaster as well for the fun of it. I went into the cabinet and he went into a ceiling return. It worked for him. </p> I would assume you tested tha…tag:homeenergypros.lbl.gov,2015-08-04:6069565:Comment:1854332015-08-04T01:28:12.715ZColin Gengehttp://homeenergypros.lbl.gov/profile/ColinGenge
<p>I would assume you tested that high air leakage from the equipment cabinet and not on a flex connected to the return? This is super important.</p>
<p>I would assume you tested that high air leakage from the equipment cabinet and not on a flex connected to the return? This is super important.</p> Interesting thought but the i…tag:homeenergypros.lbl.gov,2013-12-21:6069565:Comment:1454782013-12-21T04:05:44.713ZSean Lintow Srhttp://homeenergypros.lbl.gov/profile/sls
<p>Interesting thought but the issue with that is contractors bumping up manual J's for bigger units - the 99 occupants, leaky house, etc... tricks we have all seen used to get to there favorite 400 or 500 SF per ton. Granted commercial never sees this issue but that is because they require a mechanical engineer in many cases &amp; also have higher loads than residential due to ventilation requirements</p>
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<p>I think John has it nailed - 6% total (at final) &amp; 10% for inside…</p>
<p>Interesting thought but the issue with that is contractors bumping up manual J's for bigger units - the 99 occupants, leaky house, etc... tricks we have all seen used to get to there favorite 400 or 500 SF per ton. Granted commercial never sees this issue but that is because they require a mechanical engineer in many cases &amp; also have higher loads than residential due to ventilation requirements</p>
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<p>I think John has it nailed - 6% total (at final) &amp; 10% for inside conditioned space (especially for "balanced" systems where they have actual returns in each room) with maybe a max based on nominal airflow. Shoot to make it fair for smaller houses to promote them maybe even go 8% for homes under 1200 SF. As for reporting, I think it should be both the % but also as Ted points out - actual leakage numbers </p> Follow Up on 787 cfm at 25 to…tag:homeenergypros.lbl.gov,2013-12-21:6069565:Comment:1457362013-12-21T02:53:16.895ZJohn Nicholashttp://homeenergypros.lbl.gov/profile/JohnNicholas
<p>Follow Up on 787 cfm at 25 total leakage. Ted, 1425 sf conditioned space.</p>
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<p>The systems were installed with no tape or mastic used. This model had sheet metal trunks with sheet metal take offs; in the basement ceiling / main floor truss system. I reported this to the owner and the next week reviewed it with the owner and the HVAC Company. Two days later the owner had permission from the tenant to retest. Lots of weird looks and questions from the HVAC guys. Then I fogged the…</p>
<p>Follow Up on 787 cfm at 25 total leakage. Ted, 1425 sf conditioned space.</p>
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<p>The systems were installed with no tape or mastic used. This model had sheet metal trunks with sheet metal take offs; in the basement ceiling / main floor truss system. I reported this to the owner and the next week reviewed it with the owner and the HVAC Company. Two days later the owner had permission from the tenant to retest. Lots of weird looks and questions from the HVAC guys. Then I fogged the system. When the mech room filled with smoke the owners Reps left.</p>
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<p>The HVAC pulled the air handler and sealed it to the duct system. They also put mastic on anything they could find in the mech room. We retested and got it down to 500. The IR showed all the elbows from take offs to supplies with hot spots. We tested a 550 cfm @ 25 leakage on the same system in a slab on grade, ducts in the attic, 716 sf. Smoke showed the same problem. Same fix retest came in at 100 cfm @ 25. Pretty close to the 10% of 80. Leakage to the outside was 38 cfm at 25. Blower door on that unit was 2.9 ACH at 50.</p>
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<p>Showed the owner's Rep the Goodman manual statement requiring a tight connection to both sides of the duct system. He had seen the smoke, he knew. The HVAC guys tried to down play the requirement.</p>
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<p>They would not have had to pull the air handler in these units if they had taped them at rough-in. They are voluntarily pulling the remaining 32 units and sealing the connections from the air handler to the duct system.</p> My understanding of duct leak…tag:homeenergypros.lbl.gov,2013-12-21:6069565:Comment:1455572013-12-21T02:41:51.221ZJohn Nicholashttp://homeenergypros.lbl.gov/profile/JohnNicholas
<p>My understanding of duct leakage per sqft of conditioned floor area came out in Energy Star 3.0.</p>
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<p>The size adjustment factor, the penalty for oversizing homes with the use of a Target HERS Score were ways of making builders look at downsizing homes. So perhaps the metric of pa/sq ft was another nudge.</p>
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<p>Then It got picked up by IECC. That means it will probably take moving the mountain to somewhere for change.</p>
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<p>The ACCA have it right - Their…</p>
<p>My understanding of duct leakage per sqft of conditioned floor area came out in Energy Star 3.0.</p>
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<p>The size adjustment factor, the penalty for oversizing homes with the use of a Target HERS Score were ways of making builders look at downsizing homes. So perhaps the metric of pa/sq ft was another nudge.</p>
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<p>Then It got picked up by IECC. That means it will probably take moving the mountain to somewhere for change.</p>
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<p>The ACCA have it right - Their standard is 6% of system flow for systems with any of the duct work outside conditioned space and 10% for systems 100% within conditioned space. I believe that is total leakage. That would be a comfort thing.</p>
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